Abstract
GRB 190114C, a long and luminous burst, was detected by several satellites
and ground-based telescopes from radio wavelengths to GeV gamma-rays. In the
GeV gamma-rays, the Fermi LAT detected 48 photons above 1 GeV during the first
hundred seconds after the trigger time, and the MAGIC telescopes observed for
more than one thousand seconds very-high-energy (VHE) emission above 300 GeV.
Previous analysis of the multi-wavelength observations showed that although
these are consistent with the synchrotron forward-shock model that evolves from
a stratified stellar-wind to homogeneous ISM-like medium, photons above few
GeVs can hardly be interpreted in the synchrotron framework. In the context of
the synchrotron forward-shock model, we derive the light curves and spectra of
the synchrotron self-Compton (SSC) model in the stratified and homogeneous
medium. In particular, we study the evolution of these light curves during the
stratified-to-homogeneous afterglow transition. Using the best-fit parameters
reported for GRB 190114C we interpret the photons beyond the synchrotron limit
in the SSC framework and model its spectral energy distribution. We conclude
that low-redshift GRBs described under a favourable set of parameters as found
in the early afterglow of GRB 190114C could be detected at hundreds of GeVs,
and also afterglow transitions would allow that VHE emission could be observed
for longer periods.